The present invention generally relates to a coordinated system of vehicular and pedestrian traffic flow and traffic light control. More specifically, the present invention is an integrated model for reorganizing traffic flow and signalization on city streets to maximize safety and minimize delays without grade separation devices.
User dissatisfaction with city traffic is derived out of a variety of well-documented concerns, which, among others, include delays, cumbersome and frustrating frequency and duration of red lights encountered at street intersections, safety, and inability to efficiently integrate a third mode of transportation such as bicycles into the existing traffic management policy. Additionally, the movement of automobile and pedestrian traffic at street intersections is insufficiently resolved, and the prevailing pattern of signalized movement at street intersections is generically accident prone.
A larger problem is framed in an environment wherein the physical dimensions of existing street plans, including road geometry and land-use are fixed, and traffic composition, volume and behavior are constantly changing in a space-time continuum. The traffic planner employs street signalization and signage to manage and/or regulate traffic flow on city streets. Policing is an additional tool.
The inventor""s personal interest in the problem has resulted in several patented concepts. The xe2x80x9cMultiple Loop Systemxe2x80x9d of street circulation, hereinafter xe2x80x9cMLSxe2x80x9d, the subject of U.S. Pat. No. 4,927,288 (fully incorporated herein by reference) issued May 22, 1990, offers a simple and efficient means for eliminating the possibility of vehicle gridlock by providing for better traffic flow on existing street networks. The ""288 patent discloses a road traffic network, wherein the fundamental building block is an endless loop of one way traffic flow completely surrounded by a second endless loop having traffic flow opposite in direction to the traffic flow direction of the first loop with an interconnecting traffic flow roadway between the loops.
U.S. Pat. No. 5,092,705 (fully incorporated herein by reference) issued Mar. 3, 1992, relates to a method for minimizing conflicting flows between vehicular and pedestrian traffic on one-way intersections. In brief, the ""705 patent relates to a method for controlling the vehicular traffic light signals at intersections of avenues and crosswalks, along with xe2x80x9cWalkxe2x80x9d/xe2x80x9cDon""t Walkxe2x80x9d traffic signals for pedestrians at the crosswalks, so that the Multiple Loop System operates to its maximum efficiency, all while preserving safety and reducing intermodal conflicts.
Another patent that has relevance to the Multiple Loop System is U.S. Pat. No. 5,330,278 (fully incorporated herein by reference) issued Jul. 19, 1994. This patent teaches a system of signalization that minimizes delays by facilitating two-way progression on MLS based grid networks. Here, two phase traffic signals, red and green, of equal duration are employed at the roadway intersections in such a manner that idling time is minimized while vehicular traffic flow is maximized, all with reduced intermodal conflicts.
The above patents are interrelated and MLS based. Two recent patents, U.S. Pat. Nos. 5,821,878 and 5,959,553 (both fully incorporated herein by reference), are titled xe2x80x9cCoordinated Two Dimensional Progression Traffic Signal Systemxe2x80x9d, which is also referred to hereinafter as xe2x80x9cATBS,xe2x80x9d i.e., the xe2x80x9cAlternating Time Band Systemxe2x80x9d of street signalization. The present disclosure, referred to as xe2x80x9cATBS-2Wxe2x80x9d, develops additional algorithms that improve on disclosures of ""278, ""878 and ""553 references in the following aspects: it discloses an improved arrangement of alternating bands for two-way streets systems; it fully integrates crosswalks into the ATBS-2W signalization policy to minimize friction, and/or, to eliminate conflicting flows (at grade) at grid intersections; and it discloses a method for integrating dedicated bikeways into existing street plans, and the ATBS-2W signalization policy, for both one-way or two-way street systems.
It is an object of the present invention to provide an improved arrangement of alternating bands for two-way streets systems.
It is another object of the present invention to fully integrate crosswalks into the ATBS-2W signalization policy to minimize friction, and/or to eliminate conflicting flows (at grade) at grid intersections.
It is a further object of the present invention to provide a method for integrating dedicated bikeways into existing street plans, and the ATBS-2W signalization policy, for both one-way or two-way street systems, within the framework of a unified method for street signalization.
Other objects, advantages and features of this invention will be more apparent hereinafter.
ATBS-2W combines a variety of concepts into an integrated operating system for traffic management in cities. Design elements of ATBS-2W include a combination of dynamic checkerboard arrangements of alternating bands in paired sets of two or three bands for one-way and two-way streets respectively, recessed crosswalks, the configuration of the flow pattern for bikeways on one-way grid, opening of crosswalks on the left side of moving green bands at two-way grid intersections, placement of bikeways between the sidewalk and the parking lane, and creation of a separate phase for the movement of bicycle traffic on one-way streets. In accordance with the invention, crosswalks are preferably open either one at a time or in pairs, in tandem with green bands on two-way avenues and/or streets. On one way streets, crosswalks may also be open in pairs or, where safety is a concern, one at a time, when the traffic signal along the intersecting avenue is green. The remaining crosswalks on one-way street, will then be open during the red signal at the same intersection.
The mathematical variables in the ATBS-2W algorithm are driven by a notional value of time interval xe2x80x9cPxe2x80x9d as one constant. According to Equation 1 (see below), xe2x80x9cPxe2x80x9d is the outcome of ta, tb and ft, i.e. the travel time along one avenue block; travel time along one street block and the time delay required to make a turn. The user can determine xe2x80x9cPxe2x80x9d by assigning appropriate speeds along the avenue and the intersecting street based on traffic volume and other factors. As traffic volume increases speed tends to decline, particularly as the demand to capacity ratio (V/C) approaches unity. Since xe2x80x9cPxe2x80x9d varies inversely with speed, it and the cycle length C will increase with traffic volume, consistent with current practice. Under the present system C=3P for two-way streets, and C=2P for one-way streets.
The decision framework includes the acceptance of a method to progress traffic for both sides of two-way streets independently. An adoption of the present method opens one crosswalk only during a green phase and xe2x80x9ctwo or threexe2x80x9d crosswalks during the red phase in a xe2x80x9ctwo or three phasexe2x80x9d signal cycle, for one-way grids. The present method also integrates bicycle flow with that of the crosswalk policy on both one-way and two-way streets.
The forgoing model cannot in itself cover the full variety of street conditions, layout or network design that may be found in a global context. It does not cover the anomalies in individual behavior, changes in vehicular composition such as trucks, buses and or motorcycles; nor does it account for street congestion due to traffic accidents, delivery vehicles, and/or construction activity, etc. The combined algorithm nevertheless creates a powerful tool to develop or customize a series of ATBS-2W based stand-alone or add-on software products that may each be designed to serve a specific purpose that can include, a. Simulation studies, b. Planning studies, or c. Real Time applications (see below).
The Real Time Software based on ATBS-2W, when applied on the ground to discrete areas or zones will use network servers to regulate signal timings at street intersections via individual controllers. The signal timings will reflect actual counts of vehicular traffic on any given street grid at programmed intervals in a day or week as necessary. Traffic counts may be collected by either of two methods: a use of traffic sensors on the ground, such as loop detectors or microwave sensors, or by locking into a Global Positioning System (GPS) with communication chips that are embedded into automobiles. Individual applications will have to be custom built into xe2x80x9cReal Time Softwarexe2x80x9d derived out of the ATBS-2W algorithm for each application. The end result is that of a future development of Intelligent Street Networks (ISN). These when combined with a future use of hybrid electric vehicles, LED Signals and digital controllers, can improve energy conservation.